1. Technical Field
The present invention relates to an electronic device provided with a wiring substrate having wirings formed thereon.
2. Related Art
An electronic device includes a drive element such as a piezoelectric element to be deformed in response to an applied voltage, and the electronic device is applied to various types of devices, sensors, or the like. For example, a liquid ejecting apparatus ejects various types of liquid from a liquid ejecting head using the electronic device. Examples of the liquid ejecting apparatus include an image recording apparatus such as an ink jet printer and an ink jet plotter, but in recent years, the liquid ejecting apparatus has also been applied to various manufacturing apparatuses, by taking advantage of features that a very small amount of liquid can be accurately landed at a predetermined position. For example, the liquid ejecting apparatus has been applied to a display manufacturing apparatus that manufactures a color filter for a liquid crystal display, or the like, an electrode forming apparatus that forms electrodes in an organic electro luminescence (EL) display, a field emission display (FED), or the like, and a chip manufacturing apparatus that manufactures a bio-chip (a biochemical element). Then, a recording head for the image recording apparatus ejects liquid ink, and a color material ejecting head for the display manufacturing apparatus ejects respective color material solutions of Red (R), Green (G), and Blue (B). Further, an electrode material ejecting head for the electrode forming apparatus ejects liquid electrode materials, and a bio-organic material ejecting head for the chip manufacturing apparatus ejects a bio-organic material solution.
The liquid ejecting head includes an electronic device in which a pressure chamber formation substrate including a pressure chamber formed thereon in communication with a nozzle, a piezoelectric element (a type of a drive element) causing a pressure fluctuation in liquid inside the pressure chamber, a sealing plate spaced apart from the piezoelectric element, and the like are stacked. The piezoelectric element is driven by a drive signal supplied from a drive IC (also referred to as a driver IC). The drive IC is provided on the outside of the electronic device in the related art. For example, in the known technique, the drive IC is provided in a tape carrier package (TCP) that is connected to the electronic device (for example, see JP-A-2012-51253). A drive signal from the drive IC is supplied to the piezoelectric element through wirings formed in the TCP.
In recent years, with the miniaturization of the liquid ejecting head, a technique for bonding the drive IC on a sealing plate that covers the piezoelectric element has been developed. In this configuration, a plurality of terminals that are connected to the terminal of the drive IC are formed on a surface on one side (a drive IC side) of the sealing plate. Meanwhile, a plurality of terminals that are connected to the terminal of the piezoelectric element are formed on a surface of the other side (the opposite side of the drive IC side) of the sealing plate. The terminals formed on the surface on one side and the terminals formed on the surface of the other side are connected by a wiring formed over both surfaces of the sealing plate.
However, a center-to-center distance (pitch) of the adjacent terminals of the drive IC and the center-to-center distance (pitch) of the adjacent terminals of the piezoelectric element are unlikely to be aligned with each other for reasons of manufacturing or design. Therefore, it is considered to perform a so-called pitch conversion on one surface of the sealing plate, in which wiring is performed while gradually changing an inclination angle such that one end of a wiring, that connects the terminal on the drive IC side and the terminal on the piezoelectric element, is aligned with the pitch of the terminal on the same side as the one end, and the other end of the wiring is aligned with the pitch of the terminal on the same side as the other end. However, with an increase in the number of nozzles and a high density of nozzles, the number of terminals increases, and if the terminal pitch is narrowed, it is difficult to perform the pitch conversion without changing an interval between one terminal and the other terminal. In other words, as a wiring is positioned closer to the outside, among arranged wirings, the wiring has a steeper inclination relative to the arrangement direction of the terminal, and has difficulty in securing a sufficient wiring interval and a wiring width. If increasing the interval between the terminal on the drive IC side and the terminal on the piezoelectric element side in order to secure the wiring interval and the wiring width, the sizes of the sealing plate and the drive IC are increased, and as a result, it is difficult to miniaturize the electronic device.